The invention relates to a refractory pipeline which has several pipe sections that are exposed to nonuniform temperatures.
When a nonuniform distribution of temperature is applied to adjacent sections of ceramic pipelines, heat stresses arise in the pipelines. The stress in the pipe is attributable to sharp differences in the temperatures to which neighboring sections of the same pipe are exposed. The ceramic pipelines generally comprise an alumina material. Such a nonuniform temperature distribution may arise in areas of very steep temperature gradients within the pipe sections of tubular furnaces, tubular digesters, rotary furnaces or similar high temperature heating devices. Such temperature gradients exist, for instance, at the transition between heated zones and cooler regions of typical furnace units. The heat stresses which arise within the pipe can lead to the formation of cracks in the ceramic pipeline or, in extreme cases, to the destruction of the pipeline. The longer the pipeline or the poorer its thermal conductivity, the greater is the likelihood that formation of cracks or pipeline destruction may take place. Additional dangers arise when a furnace unit is operated intermittently, because very steep temperature gradients are created during each commencement of the intermittent operation.